As the cover material of two-piece golf balls and some wound golf balls, ionomer resins in the form of ethylene-(meth)acrylic acid copolymers have been widely used and accepted because of their long-lasting impact resistance and cut resistance. Since the ionomer resins provide hard hitting feel and high hardness as compared with the balata rubber conventionally used as the cover material, golf balls with an ionomer resin cover are said difficult to impart a desired quantity of spin and inferior to control on iron shots.
For improvements in these respects, Sullivan, U.S. Pat. No. 4,884,814 or JP-A 308577/1989 proposes to blend a hard ionomer resin in the form of an ethylene-(meth)acrylic acid copolymer having a certain spectrum of physical properties with a specific amount of a soft ionomer resin in the form of an ethylene-(meth)acrylic acid-(meth)acrylate terpolymer. The soft/hard ionomer blend is used as a golf ball cover. This is a quite effective technique for improving the hitting feel and control of golf balls using a conventional ionomer resin in the form of an ethylene-(meth)acrylic acid copolymer as the cover.
Nevertheless, the golf ball cover of the above-mentioned soft/hard ionomer blend has several problems. The cover is softer and allows the ball to receive more spin on iron shots, which means the increased frictional force between the club face and the cover. Then balls using a hard core such as two-piece solid golf balls have the likelihood that the ball surface be scraped as a consequence of iron shots because the cover surface can be peeled by grooves across the iron club face.
Due to the reduced hardness, the ionomer cover itself is less repulsive so that the ball is also substantially reduced in repulsion.
An improvement in this regard is proposed in JP-A 277208/1993. A mixture of two or more metal salts of an ethylene-unsaturated carboxylic acid-unsaturated carboxylate terpolymer having a low flexural modulus is used as the cover for the purpose of protecting the ionomer cover against scuffing by iron club shots. This technique, however, is not practical because scuffing resistance upon iron club shots is still insufficient and because of reduced repulsion.
Therefore, there is a need for a golf ball having a good feel, good repulsion, a high spin rate, easy control, and resistance to scraping or burring.
An object of the invention is to provide a golf ball meeting such requirements.